Buckeye Dairy News: Volume 8 Issue 4

Dr. Naomi Botheras, Animal Welfare Program Specialist, The Ohio State University 

Due to costs associated with the construction and maintenance of free stall barns, dairy farmers may limit the number of feeding and/or resting places available for cows to maximize utilization of facilities. Facility design, such as whether there are two or three rows of stalls per feeding line, may also influence the number of cows which have to share a particular resource. However, the impact of overcrowding on cow behavior, welfare, and productivity should be considered. At pasture, dairy cows tend to synchronize their grazing and lying behavior. That is, most cows will eat or lay down at the same time. Indoors, such synchronization may be less pronounced, but is often still evident and may be strongly influenced by management procedures, such as the delivery of fresh feed and milking. The synchronization of dairy cattle behavior, along with a limited number of feeding and/or lying places, means that not all cows will be able to eat or lay down at once.

Overcrowding free stalls

Studies which have investigated the effects on cow behavior of a limited number of free stalls found that the total lying time of cattle over a 24-h period was reduced due to overcrowding (Friend et al., 1977; Wierenga and Hopster, 1990; Leonard et al., 1996; Dippel et al., 2005). Even at relatively low overstocking rates (25% overcrowding, or 1.25 cows per free stall), Wierenga and Hopster (1990) found reductions in the total daily lying times of some cows. At low overstocking rates, the lying times of only low-ranking cows seem to be affected, while at higher overcrowding rates, the lying times of all cows are affected. Under conditions of one stall per cow, very often 90% or more of the cows are in the stalls during the night, and very few cows stand inactive in the alleys at any time throughout the day. However, time spent standing inactive in the alleys is significantly higher in overcrowded conditions, and this is particularly evident during the night. Furthermore, overcrowding may lead to cows (particularly low ranking cows) lying in the alleys at night when all stalls are occupied, but cows are highly motivated to lay down (Wierenga and Hopster, 1990; Leonard et al., 1996). This aberrant behavior has obvious implications for cow cleanliness and the risk of mastitis.

Reduced daily lying times (Colam-Ainsworth et al., 1989; Leonard et al., 1994, 1996; Chaplin et al., 2000) and increased time standing on hard surfaces (Greenough and Vermunt, 1991; Singh et al., 1993) are behaviors that have been associated with increased rates of hoof lesions and lameness. Hence, a reduction in lying time (and consequently increased time spent standing in the alleys) due to overcrowding may increase the risk of lameness, with obvious implications for cow welfare and productivity. Furthermore, adequate rest is necessary to ensure high production, and blood flow to the udder is increased when cows are lying down. Cows also tend to ruminate (chew their cud) when lying down compared to when standing up, so maximizing lying time is also important for optimizing rumination time. Disturbed rest leads to physiological changes in cattle that are usually indicative of stress and which are likely to affect cow health and milk production. Therefore, to maintain high levels of production, health, and welfare, it is essential that dairy cows are able to optimize their time spent resting.

Overcrowding the feeding area

Friend et al. (1977) found that time spent eating was not reduced until only 0.1 m of feeding space per cow was provided (space allowance ranged from 0.5 m to 0.1 m per cow), and Collis et al. (1980) found total feeding time did not change when feeding space was gradually reduced from 1.05 m to 0.15 m per cow. Similarly, Wierenga and Hopster (1990) found that overcrowding the number of feeding places by 25 to 55% had almost no consequences on eating time. It was suggested that the limited effect of overcrowding on total eating time may be due to the relatively short amount of time that cows spend eating each day (around 4 hours), which would enable a cow to easily compensate for changes in the opportunity to eat that occur due to overcrowding.

However, in contrast to findings from earlier studies, more recent research by DeVries et al. (2004) found that when cows had access to more feeding space (1.0 m vs. 0.5 m of feeding space per cow), cows increased their feeding activity throughout the day and especially during the 90 min after fresh feed was provided. At 30% overcrowding of headlocks (1.3 cows per headlock), Batchelder (2000) found reduced daily dry matter intakes and substantially fewer cows eating during both the hour following milking and following delivery of fresh feed. Interestingly, Batchelder (2000) also found that overcrowded cows spent significantly less time ruminating during a 24-h period than did cows that were not overcrowded. Huzzey et al. (2006) found that for both post-and-rail and headlock feed barriers, overcrowding resulted in reduced feeding times and increased time spent standing inactive in the feeding area. These changes were most obvious during the times of peak feeding activity (within 60 min following the delivery of fresh feed). Mentink and Cook (2006) compared free stall pens with 2 or 3 rows of stalls per pen, which provide for very different amounts of feed space per cow when free stalls are stocked at similar rates. These authors found that the extra feed space per cow in a 2-row pen improved access to feed at peak feeding times.

All cows are motivated to access feed when fresh feed is delivered, but when feeding space is inadequate, some cows may be prevented from feeding at the time of fresh feed delivery, and consequently, may be forced to shift their feeding time. Research has indicated that cows will sort a TMR, and hence feed quality declines throughout the day. Thus, cows that are forced to delay their feeding time due to overcrowding may consume a poorer quality diet. Furthermore, when cows do not have access to feed when they want to eat, they may over-eat following a period of feed deprivation. This could happen when cows have limited access to feed because of overstocking. Increased feeding competition may reduce intake and increase feeding rate, possibly increasing the risk for metabolic problems, such as left displaced abomasums and subacute ruminal acidosis (Shaver, 1997, 2002). Increased aggression in the feeding area when cows are overcrowded has also been noted (Olofsson, 1999; DeVries et al., 2004; Huzzey et al., 2006). Aggression could have consequences for hoof lesion development and lameness. Shaver (2002) also suggested that the potential for laminitis may be greater when overcrowding of free stalls coincides with limited feeding space (as is often the case), because cows may spend more time standing on concrete rather than lying in stalls, and consume fewer, but larger, meals, or have reduced feed intake.

It is important to realize that even when free stalls are not overstocked, social and environmental factors may still reduce the number of available or preferred resting places. For example, stalls in some locations may not be used due to close proximity to a water trough or high volume of cow traffic, or because they are located in a draft. Low-ranking cows will also prefer not to use a stall adjacent to a higher-ranking cow, and a cow lying in a stall may occupy part of a neighboring stall with their legs, head, or back, which would prevent another cow from lying down in the vacant stall. Thus, the implications of overstocking resting and/or feeding areas for cow behavior, health, production, and welfare should be carefully considered.

*A complete list of research references is available on request.

Mrs. Dianne Shoemaker, Extension Dairy Specialist, OSU Extension Center at Wooster 

Hot environmental temperatures, combined with high humidity, can negatively impact colostrum production in first calf heifers. Conversely, heat treatment of colostrum can have more than one benefit according to data presented at the 2006 American Dairy Science Association (ADSA) Annual Meetings.

Generous colostrum feeding guidelines ensure that most calves will receive sufficient immunoglobulins (IgG; antibodies) to achieve a successful transfer of immunity. Success depends on the individual calf's ability to absorb IgG and the calf being fed enough IgG. We know that the calf's ability to absorb antibodies is negatively effected by the time that has elapsed since birth and the relative difficulty of the birth process. While absorption rates can approach 50% shortly after birth, they decline rapidly towards zero within the first 24 hours.

Environmental heat

Heat stress of first calf heifers is likely to cause a drop in IgG concentrations in their first milking. An Italian study using 12 Holstein heifers kept in environmentally controlled rooms reported a 19% decrease in IgG production from the heifers exposed to higher temperatures (89°F daytime and 79°F nighttime) compared to the control heifers (65°F, all heifers experienced 72% relative humidity.) Heifers were exposed to these environments for approximately 3 weeks before calving.

Is this happening with your heifers? The only way to know for sure is to measure the IgG concentrations in each dam's colostrum before feeding it to the calf. In the Italian study, yield (volume) of colostrum did not differ between heifers subjected to heat stress and the control heifers. Evaluating quality of colostrum based on volume produced will be useless. Simple on-farm methods of quality evaluation include using either a colostrometer or commercial "quick tests". These tools are readily available from farm supply catalogs or stores.

Heat treatment

Pasteurization of colostrum is generating increased interest as herds seek additional tools to control the transfer of disease pathogens, such as Johne's bacteria, through colostrum.
Godden at the University of Minnesota reported new data at this year's ADSA meeting from a study on the impact of pasteurizing colostrum on the apparent efficiency of IgG absorption.

Early attempts at pasteurization of colostrum were frustrating as the HTST (high temp, short time) pasteurization methods created a pudding like mass that plugged up the equipment and was impossible to feed. Longer time, lower temp methods are more successful, although some thickening can also occur.

Two important questions are: "Will the heat treatment harm the IgG?" and "Will pasteurization impede a successful transfer of immunity?" To help answer these questions, batches of colostrum were divided in half. Using a 60 min, 140oF pasteurization method, one half of the batch was pasteurized and one half of each batch was not. Pairs of calves were fed either the pasteurized or the fresh colostrum.

All fifty calves achieved a successful passive transfer of immunity. However, calves fed the pasteurized colostrum achieved significantly higher blood IgG concentrations than the calves fed fresh colostrum (22.3 mg/ml for pasteurized and 17.5 mg/ml for fresh). After calves were tested for blood IgG levels, the apparent efficiency of absorptions were calculated. Calves fed the fresh colostrum averaged 27% apparent absorption, while calves fed pasteurized colostrum averaged 35%.

Bottom line, the higher the efficiency of absorption, the better chance a calf has to achieve a successful transfer of passive immunity. Based on this study, the pasteurization process not only did not reduce the IgG concentration in colostrum, but the bacteria "kill" of the pasteurization appeared to allow more IgG to be absorbed compared to unpasteurized colostrum.

It has been demonstrated that bacteria that get into the calf's gut before colostrum is fed can interfere with IgG absorption. This study provided a strong indicator that bacteria may interfere with IgG absorption when they are fed with the colostrum as well. Dairy farms must have protocols and practices in place to ensure that colostrum is harvested and handled as cleanly as possible.

*A list of research references is available on request.

Dr. William B. Epperson, Extension Dairy Veterinarian, The Ohio State University 

Mastitis is generally regarded as the most costly infectious disease on dairy farms. For most farms, the main bacteria causing mastitis have shifted to the environmental bacteria (coliforms and environmental streptococci), which are transferred to teat ends at times other than milking.

The dry period is an important time for the establishment of environmental intramammary infection (IMI). Of environmental streptococci IMI present in lactation, 50.5% originated in the non-lactating period (Todhunter et al., 1995). Similarly, 61.2% of clinical coliform mastitis cases observed in lactation were due to organisms that originated with infection in the dry period (Todhunter et al., 1991). Together, these facts emphasize the relative importance of the dry period on mammary gland health.

Within the traditional 8 week dry period, the first 2 weeks and the last 2 weeks have been shown to be high risk times for new IMI (Smith et al., 1985). These times are the transitions into and out of involution, and are accompanied by high volumes of milk/colostrum in the gland. Therefore, preventive strategies that impact either or both of these high risk times are likely to be beneficial.

Numerous field studies have related high environmental bacterial loads to increased mastitis. Providing a clean, comfortable dry cow environment will decrease teat end exposure to pathogens. Inorganic bedding materials support lower bacterial loads, improving hygiene and leading to improved udder health. Cracked skin on teat ends, as commonly seen with hyperkeratotic teat ends (often termed "teat rings", "prolapsed sphincters" or the like) has been shown to increase risk of IMI in the dry period, probably by promoting bacterial colonization (Dingwell et al., 1994).

Teat canal plug formation following dry off is an important event in limiting movement of bacteria into the mammary gland. Due to intramammary pressure immediately after dry off, the teat canal is forced to dilate. Epithelial cells accumulate and fill the canal, causing constriction over 1 to 2 weeks (Dingwell et al., 2003). If these cells are not removed, the canal eventually seals closed. Teat canals that remain open in the dry period are almost twice as likely to acquire a new IMI. A recent study indicated that about 50% of teat canals close in the first week. However, by the 6th week, only 77% were closed, suggesting a considerable fraction of quarters remained open in the dry period.

Factors which impact teat canal closure are not known, but presumable include milk yield, teat shape and anatomy, and trauma. Recent work has indicated that milk production of > 46 lb/day the day prior to dry off was associated with a delay in teat canal closure. A preliminary report from Ohio indicted that with each 11 lb/day increase in milk production above 27.5 lb on the day prior to dry off, IMI at calving increased 77% (Rajala-Schltz et al., 2005). Future udder health programs may include specific recommendations for managed decrease of milk production immediately prior to dry off in an effort to improve teat canal closure and limit dry period IMI.

Teat canal sealing products were devised to lessen the impact of delayed teat canal closure. Administration of the internal teat sealant (Orbeseal®, Pfizer Animal Health) has been shown to decrease new IMI at calving by approximately 30% (Godden et al., 2003). In addition, reductions of clinical mastitis and early lactation somatic cell counts have been observed in some studies. External teat sealers are specially formulated teat dips intended to produce a film barrier on the teat skin. No work with these products has been reported in scientific journals. While the internal teat sealer has been shown effective and is broadly recommended (concurrent with dry cow therapy), external teat sealers have not undergone the same study and scrutiny, and therefore, are not universally recommended at this time.

Optimal nutrition promotes host defense and contributes to the overall well-being of the cow and the mammary gland. The benefit of adequate levels of vitamin E (1000 mg/head/day in diet) and selenium (minimum of 0.3 ppm in diet) in mammary health are well known (Hogan et al., 1993). Dry and transition cows with energy imbalance will often express ketosis shortly after calving. Cows with ketosis within 1 week after calving have an increased risk of clinical mastitis in the period from calving to 63 days in milk (Leslie et al., 2001). Cows with postpartum metritis show a tendency for increased susceptibility to subsequent IMI (Epperson et al., 1993). As each of these conditions (mastitis, ketosis, and metritis) is associated with decreased white blood cell function, the occurrence of one disease identifies those cows at risk of other diseases.

Antibiotic therapy of all quarters of all cows at dry off (total dry cow therapy; DCT) has been a longstanding recommendation for US dairy producers. This is based on the following facts:

1) DCT will help eliminate a high proportion of existing IMI caused by Streptococcus agalactiae, C. bovis, and coagulase negative staphylococci (Dingwell et al., 2003),
2) DCT enhances the cure rate of Staphylococcus aureus (Dingwell et al., 2003),
3) Available evidence indicates that DCT will prevent new environmental streptococcal IMI from establishing in the early dry period (Smith et al., 1985), and
4) There is no substantial evidence to indicate that antimicrobial resistance in mastitis pathogens is emerging in a widespread manner as a consequence of DCT (National Mastitis Council, 2004).

Present day DCT products are active principally in the first weeks of the dry period. Antimicrobial activity declines to negligible levels by the final 2 weeks of the dry period. The cost:benefit of DCT continues to be re-evaluated, and new products/techniques may offer alternatives to DCT. However, until that time, total DCT is recommended.

*A complete list of research references is available on request.

Ms. Kim Haines, Communications Manager, ADADC Mid East

The American Dairy Association & Dairy Council (ADADC) Mid East is the local dairy farmer-funded promotion organization responsible for increasing demand for milk and dairy products. We work closely with Dairy Management, Inc., the national dairy promotion organization, to implement advertising, promotion, education, and research programs nationwide.

The ADADC Mid East recognizes that dairy farmers have a strong voice within their communities and are pleased to provide materials to assist with local dairy and agricultural promotions. Some of these materials include pencils, key chains, bumper stickers, posters, and brochures.
Materials are free to dairy farmers, princesses, and processors within the ADADC Mid East territory. Materials are also available at no charge to agriculture Extension educators and agriculture-related organizations who are conducting dairy or agriculture promotions. To order these items, please visit www.drink-milk.com or call 1-800-292-MILK.